[joulseenjoync]

I'm no scholar either but just some recommendations I have

1) Firstly I would suggest to try and find a suitable gym where there is no mixing
2) If non are available, try to make sure that the gym you go to is at the least male dominated, which shouldn't be difficult.
3) avoid gyms which tend to have a lot of dance classes (franchised gyms) and such as they are more female focused and the dress code is usually very liberal. This might make it challenging to lower your gaze.
4) check your intentions
5) weigh the benefits/consequences
6) pray istikhara before deciding

and Allah know best